I was a sixth grade alien #3 I lost my grandfather's brain

This book was really fun. because I really love alien storys. I had one question about the story but it didn't have a solution. the question was why does brianna want to steal pleskit's grandfather's brain.by the way. the characters are pleskit the alien. tim and brianna. my favorite part was when brianna tried to steal pleskit's grandfather's brain but pleskit zapped her with his alien powers!